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OpenCloudOS-Kernel/crypto/hctr2.c

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// SPDX-License-Identifier: GPL-2.0
/*
* HCTR2 length-preserving encryption mode
*
* Copyright 2021 Google LLC
*/
/*
* HCTR2 is a length-preserving encryption mode that is efficient on
* processors with instructions to accelerate AES and carryless
* multiplication, e.g. x86 processors with AES-NI and CLMUL, and ARM
* processors with the ARMv8 crypto extensions.
*
* For more details, see the paper: "Length-preserving encryption with HCTR2"
* (https://eprint.iacr.org/2021/1441.pdf)
*/
#include <crypto/internal/cipher.h>
#include <crypto/internal/hash.h>
#include <crypto/internal/skcipher.h>
#include <crypto/polyval.h>
#include <crypto/scatterwalk.h>
#include <linux/module.h>
#define BLOCKCIPHER_BLOCK_SIZE 16
/*
* The specification allows variable-length tweaks, but Linux's crypto API
* currently only allows algorithms to support a single length. The "natural"
* tweak length for HCTR2 is 16, since that fits into one POLYVAL block for
* the best performance. But longer tweaks are useful for fscrypt, to avoid
* needing to derive per-file keys. So instead we use two blocks, or 32 bytes.
*/
#define TWEAK_SIZE 32
struct hctr2_instance_ctx {
struct crypto_cipher_spawn blockcipher_spawn;
struct crypto_skcipher_spawn xctr_spawn;
struct crypto_shash_spawn polyval_spawn;
};
struct hctr2_tfm_ctx {
struct crypto_cipher *blockcipher;
struct crypto_skcipher *xctr;
struct crypto_shash *polyval;
u8 L[BLOCKCIPHER_BLOCK_SIZE];
int hashed_tweak_offset;
/*
* This struct is allocated with extra space for two exported hash
* states. Since the hash state size is not known at compile-time, we
* can't add these to the struct directly.
*
* hashed_tweaklen_divisible;
* hashed_tweaklen_remainder;
*/
};
struct hctr2_request_ctx {
u8 first_block[BLOCKCIPHER_BLOCK_SIZE];
u8 xctr_iv[BLOCKCIPHER_BLOCK_SIZE];
struct scatterlist *bulk_part_dst;
struct scatterlist *bulk_part_src;
struct scatterlist sg_src[2];
struct scatterlist sg_dst[2];
/*
* Sub-request sizes are unknown at compile-time, so they need to go
* after the members with known sizes.
*/
union {
struct shash_desc hash_desc;
struct skcipher_request xctr_req;
} u;
/*
* This struct is allocated with extra space for one exported hash
* state. Since the hash state size is not known at compile-time, we
* can't add it to the struct directly.
*
* hashed_tweak;
*/
};
static inline u8 *hctr2_hashed_tweaklen(const struct hctr2_tfm_ctx *tctx,
bool has_remainder)
{
u8 *p = (u8 *)tctx + sizeof(*tctx);
if (has_remainder) /* For messages not a multiple of block length */
p += crypto_shash_statesize(tctx->polyval);
return p;
}
static inline u8 *hctr2_hashed_tweak(const struct hctr2_tfm_ctx *tctx,
struct hctr2_request_ctx *rctx)
{
return (u8 *)rctx + tctx->hashed_tweak_offset;
}
/*
* The input data for each HCTR2 hash step begins with a 16-byte block that
* contains the tweak length and a flag that indicates whether the input is evenly
* divisible into blocks. Since this implementation only supports one tweak
* length, we precompute the two hash states resulting from hashing the two
* possible values of this initial block. This reduces by one block the amount of
* data that needs to be hashed for each encryption/decryption
*
* These precomputed hashes are stored in hctr2_tfm_ctx.
*/
static int hctr2_hash_tweaklen(struct hctr2_tfm_ctx *tctx, bool has_remainder)
{
SHASH_DESC_ON_STACK(shash, tfm->polyval);
__le64 tweak_length_block[2];
int err;
shash->tfm = tctx->polyval;
memset(tweak_length_block, 0, sizeof(tweak_length_block));
tweak_length_block[0] = cpu_to_le64(TWEAK_SIZE * 8 * 2 + 2 + has_remainder);
err = crypto_shash_init(shash);
if (err)
return err;
err = crypto_shash_update(shash, (u8 *)tweak_length_block,
POLYVAL_BLOCK_SIZE);
if (err)
return err;
return crypto_shash_export(shash, hctr2_hashed_tweaklen(tctx, has_remainder));
}
static int hctr2_setkey(struct crypto_skcipher *tfm, const u8 *key,
unsigned int keylen)
{
struct hctr2_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
u8 hbar[BLOCKCIPHER_BLOCK_SIZE];
int err;
crypto_cipher_clear_flags(tctx->blockcipher, CRYPTO_TFM_REQ_MASK);
crypto_cipher_set_flags(tctx->blockcipher,
crypto_skcipher_get_flags(tfm) &
CRYPTO_TFM_REQ_MASK);
err = crypto_cipher_setkey(tctx->blockcipher, key, keylen);
if (err)
return err;
crypto_skcipher_clear_flags(tctx->xctr, CRYPTO_TFM_REQ_MASK);
crypto_skcipher_set_flags(tctx->xctr,
crypto_skcipher_get_flags(tfm) &
CRYPTO_TFM_REQ_MASK);
err = crypto_skcipher_setkey(tctx->xctr, key, keylen);
if (err)
return err;
memset(hbar, 0, sizeof(hbar));
crypto_cipher_encrypt_one(tctx->blockcipher, hbar, hbar);
memset(tctx->L, 0, sizeof(tctx->L));
tctx->L[0] = 0x01;
crypto_cipher_encrypt_one(tctx->blockcipher, tctx->L, tctx->L);
crypto_shash_clear_flags(tctx->polyval, CRYPTO_TFM_REQ_MASK);
crypto_shash_set_flags(tctx->polyval, crypto_skcipher_get_flags(tfm) &
CRYPTO_TFM_REQ_MASK);
err = crypto_shash_setkey(tctx->polyval, hbar, BLOCKCIPHER_BLOCK_SIZE);
if (err)
return err;
memzero_explicit(hbar, sizeof(hbar));
return hctr2_hash_tweaklen(tctx, true) ?: hctr2_hash_tweaklen(tctx, false);
}
static int hctr2_hash_tweak(struct skcipher_request *req)
{
struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
const struct hctr2_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
struct hctr2_request_ctx *rctx = skcipher_request_ctx(req);
struct shash_desc *hash_desc = &rctx->u.hash_desc;
int err;
bool has_remainder = req->cryptlen % POLYVAL_BLOCK_SIZE;
hash_desc->tfm = tctx->polyval;
err = crypto_shash_import(hash_desc, hctr2_hashed_tweaklen(tctx, has_remainder));
if (err)
return err;
err = crypto_shash_update(hash_desc, req->iv, TWEAK_SIZE);
if (err)
return err;
// Store the hashed tweak, since we need it when computing both
// H(T || N) and H(T || V).
return crypto_shash_export(hash_desc, hctr2_hashed_tweak(tctx, rctx));
}
static int hctr2_hash_message(struct skcipher_request *req,
struct scatterlist *sgl,
u8 digest[POLYVAL_DIGEST_SIZE])
{
static const u8 padding[BLOCKCIPHER_BLOCK_SIZE] = { 0x1 };
struct hctr2_request_ctx *rctx = skcipher_request_ctx(req);
struct shash_desc *hash_desc = &rctx->u.hash_desc;
const unsigned int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE;
struct sg_mapping_iter miter;
unsigned int remainder = bulk_len % BLOCKCIPHER_BLOCK_SIZE;
int i;
int err = 0;
int n = 0;
sg_miter_start(&miter, sgl, sg_nents(sgl),
SG_MITER_FROM_SG | SG_MITER_ATOMIC);
for (i = 0; i < bulk_len; i += n) {
sg_miter_next(&miter);
n = min_t(unsigned int, miter.length, bulk_len - i);
err = crypto_shash_update(hash_desc, miter.addr, n);
if (err)
break;
}
sg_miter_stop(&miter);
if (err)
return err;
if (remainder) {
err = crypto_shash_update(hash_desc, padding,
BLOCKCIPHER_BLOCK_SIZE - remainder);
if (err)
return err;
}
return crypto_shash_final(hash_desc, digest);
}
static int hctr2_finish(struct skcipher_request *req)
{
struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
const struct hctr2_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
struct hctr2_request_ctx *rctx = skcipher_request_ctx(req);
u8 digest[POLYVAL_DIGEST_SIZE];
struct shash_desc *hash_desc = &rctx->u.hash_desc;
int err;
// U = UU ^ H(T || V)
// or M = MM ^ H(T || N)
hash_desc->tfm = tctx->polyval;
err = crypto_shash_import(hash_desc, hctr2_hashed_tweak(tctx, rctx));
if (err)
return err;
err = hctr2_hash_message(req, rctx->bulk_part_dst, digest);
if (err)
return err;
crypto_xor(rctx->first_block, digest, BLOCKCIPHER_BLOCK_SIZE);
// Copy U (or M) into dst scatterlist
scatterwalk_map_and_copy(rctx->first_block, req->dst,
0, BLOCKCIPHER_BLOCK_SIZE, 1);
return 0;
}
static void hctr2_xctr_done(struct crypto_async_request *areq,
int err)
{
struct skcipher_request *req = areq->data;
if (!err)
err = hctr2_finish(req);
skcipher_request_complete(req, err);
}
static int hctr2_crypt(struct skcipher_request *req, bool enc)
{
struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
const struct hctr2_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
struct hctr2_request_ctx *rctx = skcipher_request_ctx(req);
u8 digest[POLYVAL_DIGEST_SIZE];
int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE;
int err;
// Requests must be at least one block
if (req->cryptlen < BLOCKCIPHER_BLOCK_SIZE)
return -EINVAL;
// Copy M (or U) into a temporary buffer
scatterwalk_map_and_copy(rctx->first_block, req->src,
0, BLOCKCIPHER_BLOCK_SIZE, 0);
// Create scatterlists for N and V
rctx->bulk_part_src = scatterwalk_ffwd(rctx->sg_src, req->src,
BLOCKCIPHER_BLOCK_SIZE);
rctx->bulk_part_dst = scatterwalk_ffwd(rctx->sg_dst, req->dst,
BLOCKCIPHER_BLOCK_SIZE);
// MM = M ^ H(T || N)
// or UU = U ^ H(T || V)
err = hctr2_hash_tweak(req);
if (err)
return err;
err = hctr2_hash_message(req, rctx->bulk_part_src, digest);
if (err)
return err;
crypto_xor(digest, rctx->first_block, BLOCKCIPHER_BLOCK_SIZE);
// UU = E(MM)
// or MM = D(UU)
if (enc)
crypto_cipher_encrypt_one(tctx->blockcipher, rctx->first_block,
digest);
else
crypto_cipher_decrypt_one(tctx->blockcipher, rctx->first_block,
digest);
// S = MM ^ UU ^ L
crypto_xor(digest, rctx->first_block, BLOCKCIPHER_BLOCK_SIZE);
crypto_xor_cpy(rctx->xctr_iv, digest, tctx->L, BLOCKCIPHER_BLOCK_SIZE);
// V = XCTR(S, N)
// or N = XCTR(S, V)
skcipher_request_set_tfm(&rctx->u.xctr_req, tctx->xctr);
skcipher_request_set_crypt(&rctx->u.xctr_req, rctx->bulk_part_src,
rctx->bulk_part_dst, bulk_len,
rctx->xctr_iv);
skcipher_request_set_callback(&rctx->u.xctr_req,
req->base.flags,
hctr2_xctr_done, req);
return crypto_skcipher_encrypt(&rctx->u.xctr_req) ?:
hctr2_finish(req);
}
static int hctr2_encrypt(struct skcipher_request *req)
{
return hctr2_crypt(req, true);
}
static int hctr2_decrypt(struct skcipher_request *req)
{
return hctr2_crypt(req, false);
}
static int hctr2_init_tfm(struct crypto_skcipher *tfm)
{
struct skcipher_instance *inst = skcipher_alg_instance(tfm);
struct hctr2_instance_ctx *ictx = skcipher_instance_ctx(inst);
struct hctr2_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
struct crypto_skcipher *xctr;
struct crypto_cipher *blockcipher;
struct crypto_shash *polyval;
unsigned int subreq_size;
int err;
xctr = crypto_spawn_skcipher(&ictx->xctr_spawn);
if (IS_ERR(xctr))
return PTR_ERR(xctr);
blockcipher = crypto_spawn_cipher(&ictx->blockcipher_spawn);
if (IS_ERR(blockcipher)) {
err = PTR_ERR(blockcipher);
goto err_free_xctr;
}
polyval = crypto_spawn_shash(&ictx->polyval_spawn);
if (IS_ERR(polyval)) {
err = PTR_ERR(polyval);
goto err_free_blockcipher;
}
tctx->xctr = xctr;
tctx->blockcipher = blockcipher;
tctx->polyval = polyval;
BUILD_BUG_ON(offsetofend(struct hctr2_request_ctx, u) !=
sizeof(struct hctr2_request_ctx));
subreq_size = max(sizeof_field(struct hctr2_request_ctx, u.hash_desc) +
crypto_shash_descsize(polyval),
sizeof_field(struct hctr2_request_ctx, u.xctr_req) +
crypto_skcipher_reqsize(xctr));
tctx->hashed_tweak_offset = offsetof(struct hctr2_request_ctx, u) +
subreq_size;
crypto_skcipher_set_reqsize(tfm, tctx->hashed_tweak_offset +
crypto_shash_statesize(polyval));
return 0;
err_free_blockcipher:
crypto_free_cipher(blockcipher);
err_free_xctr:
crypto_free_skcipher(xctr);
return err;
}
static void hctr2_exit_tfm(struct crypto_skcipher *tfm)
{
struct hctr2_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
crypto_free_cipher(tctx->blockcipher);
crypto_free_skcipher(tctx->xctr);
crypto_free_shash(tctx->polyval);
}
static void hctr2_free_instance(struct skcipher_instance *inst)
{
struct hctr2_instance_ctx *ictx = skcipher_instance_ctx(inst);
crypto_drop_cipher(&ictx->blockcipher_spawn);
crypto_drop_skcipher(&ictx->xctr_spawn);
crypto_drop_shash(&ictx->polyval_spawn);
kfree(inst);
}
static int hctr2_create_common(struct crypto_template *tmpl,
struct rtattr **tb,
const char *xctr_name,
const char *polyval_name)
{
u32 mask;
struct skcipher_instance *inst;
struct hctr2_instance_ctx *ictx;
struct skcipher_alg *xctr_alg;
struct crypto_alg *blockcipher_alg;
struct shash_alg *polyval_alg;
char blockcipher_name[CRYPTO_MAX_ALG_NAME];
int len;
int err;
err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask);
if (err)
return err;
inst = kzalloc(sizeof(*inst) + sizeof(*ictx), GFP_KERNEL);
if (!inst)
return -ENOMEM;
ictx = skcipher_instance_ctx(inst);
/* Stream cipher, xctr(block_cipher) */
err = crypto_grab_skcipher(&ictx->xctr_spawn,
skcipher_crypto_instance(inst),
xctr_name, 0, mask);
if (err)
goto err_free_inst;
xctr_alg = crypto_spawn_skcipher_alg(&ictx->xctr_spawn);
err = -EINVAL;
if (strncmp(xctr_alg->base.cra_name, "xctr(", 5))
goto err_free_inst;
len = strscpy(blockcipher_name, xctr_alg->base.cra_name + 5,
sizeof(blockcipher_name));
if (len < 1)
goto err_free_inst;
if (blockcipher_name[len - 1] != ')')
goto err_free_inst;
blockcipher_name[len - 1] = 0;
/* Block cipher, e.g. "aes" */
err = crypto_grab_cipher(&ictx->blockcipher_spawn,
skcipher_crypto_instance(inst),
blockcipher_name, 0, mask);
if (err)
goto err_free_inst;
blockcipher_alg = crypto_spawn_cipher_alg(&ictx->blockcipher_spawn);
/* Require blocksize of 16 bytes */
err = -EINVAL;
if (blockcipher_alg->cra_blocksize != BLOCKCIPHER_BLOCK_SIZE)
goto err_free_inst;
/* Polyval ε-∆U hash function */
err = crypto_grab_shash(&ictx->polyval_spawn,
skcipher_crypto_instance(inst),
polyval_name, 0, mask);
if (err)
goto err_free_inst;
polyval_alg = crypto_spawn_shash_alg(&ictx->polyval_spawn);
/* Ensure Polyval is being used */
err = -EINVAL;
if (strcmp(polyval_alg->base.cra_name, "polyval") != 0)
goto err_free_inst;
/* Instance fields */
err = -ENAMETOOLONG;
if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME, "hctr2(%s)",
blockcipher_alg->cra_name) >= CRYPTO_MAX_ALG_NAME)
goto err_free_inst;
if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
"hctr2_base(%s,%s)",
xctr_alg->base.cra_driver_name,
polyval_alg->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
goto err_free_inst;
inst->alg.base.cra_blocksize = BLOCKCIPHER_BLOCK_SIZE;
inst->alg.base.cra_ctxsize = sizeof(struct hctr2_tfm_ctx) +
polyval_alg->statesize * 2;
inst->alg.base.cra_alignmask = xctr_alg->base.cra_alignmask |
polyval_alg->base.cra_alignmask;
/*
* The hash function is called twice, so it is weighted higher than the
* xctr and blockcipher.
*/
inst->alg.base.cra_priority = (2 * xctr_alg->base.cra_priority +
4 * polyval_alg->base.cra_priority +
blockcipher_alg->cra_priority) / 7;
inst->alg.setkey = hctr2_setkey;
inst->alg.encrypt = hctr2_encrypt;
inst->alg.decrypt = hctr2_decrypt;
inst->alg.init = hctr2_init_tfm;
inst->alg.exit = hctr2_exit_tfm;
inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(xctr_alg);
inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(xctr_alg);
inst->alg.ivsize = TWEAK_SIZE;
inst->free = hctr2_free_instance;
err = skcipher_register_instance(tmpl, inst);
if (err) {
err_free_inst:
hctr2_free_instance(inst);
}
return err;
}
static int hctr2_create_base(struct crypto_template *tmpl, struct rtattr **tb)
{
const char *xctr_name;
const char *polyval_name;
xctr_name = crypto_attr_alg_name(tb[1]);
if (IS_ERR(xctr_name))
return PTR_ERR(xctr_name);
polyval_name = crypto_attr_alg_name(tb[2]);
if (IS_ERR(polyval_name))
return PTR_ERR(polyval_name);
return hctr2_create_common(tmpl, tb, xctr_name, polyval_name);
}
static int hctr2_create(struct crypto_template *tmpl, struct rtattr **tb)
{
const char *blockcipher_name;
char xctr_name[CRYPTO_MAX_ALG_NAME];
blockcipher_name = crypto_attr_alg_name(tb[1]);
if (IS_ERR(blockcipher_name))
return PTR_ERR(blockcipher_name);
if (snprintf(xctr_name, CRYPTO_MAX_ALG_NAME, "xctr(%s)",
blockcipher_name) >= CRYPTO_MAX_ALG_NAME)
return -ENAMETOOLONG;
return hctr2_create_common(tmpl, tb, xctr_name, "polyval");
}
static struct crypto_template hctr2_tmpls[] = {
{
/* hctr2_base(xctr_name, polyval_name) */
.name = "hctr2_base",
.create = hctr2_create_base,
.module = THIS_MODULE,
}, {
/* hctr2(blockcipher_name) */
.name = "hctr2",
.create = hctr2_create,
.module = THIS_MODULE,
}
};
static int __init hctr2_module_init(void)
{
return crypto_register_templates(hctr2_tmpls, ARRAY_SIZE(hctr2_tmpls));
}
static void __exit hctr2_module_exit(void)
{
return crypto_unregister_templates(hctr2_tmpls,
ARRAY_SIZE(hctr2_tmpls));
}
subsys_initcall(hctr2_module_init);
module_exit(hctr2_module_exit);
MODULE_DESCRIPTION("HCTR2 length-preserving encryption mode");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS_CRYPTO("hctr2");
MODULE_IMPORT_NS(CRYPTO_INTERNAL);
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